Passive optical networks (PONs) can be utilized to provide data from one or more user nodes (e.g., an optical network unit [ONU], optical network terminal [ONT], etc.) to a central node (e.g., a central office, such as or including an optical line terminal [OLT]) using optical signal media (e.g., a fiber optic cable, a fiber optic link, etc.). In some PONs, time-division multiplexing (TDM) is used so that multiple bit streams or data signals (e.g., data packets) are alternately transmitted by one or more ONUs over a single communication channel. That is, in PONs employing TDM, a first ONU can transmit optical data during an allocated or predetermined time slot, and a second ONU can transmit optical data over the same media in the next allocated or predetermined time slot.
For a data packet to be accurately received by the OLT (e.g., including a burst mode optical receiver), a decision threshold must be set. That is, based on the amplitude or common-mode voltage of the received data signal, a decision threshold is set, where data having an amplitude above the decision threshold are considered to have a binary logic high state, and data having an amplitude below the decision threshold are considered to have a binary logic low state.
In some PONs, situations arise where a first ONU transmits optical data during a predetermined time slot to a receiver, and a second transmitter (e.g., a “rogue” transmitter) also transmits data to the receiver during the same predetermined time slot. For example, prior to transmission, the second transmitter may have improperly processed a data or control signal (e.g., from an external host) configured to place the ONU in a silent (e.g., a non-transmission) state. Alternatively, a hardware failure may have prevented the second ONU from switching to or remaining in a silent state. In either situation, the optical data signal transmitted by the first ONU may be incorrectly processed when data from the second ONU is also transmitted during the predetermined time slot. For example, some of the data received by the first ONU may be erroneously considered to have a high binary logic state (i.e., an amplitude above a decision threshold) when data received by the second, rogue transmitter has a high binary logic state.
Additionally, situations arise when a first ONU is transmitting optical data to the OLT during a predetermined time slot, but the optical data is improperly received due to noise introduced in the PON. Current OLTs cannot identify or distinguish a noise spike or a rogue data transmission received during a predetermined time slot from data transmitted from an authorized ONU during the predetermined time slot. Thus, for example, a noise spike having an amplitude above the decision threshold may be introduced in the PON during a predetermined time slot. The noise spike may be incorrectly processed as data having a binary logic high state (e.g., a binary “1” data bit) and provided by an authorized ONU configured to transmit data during the predetermined time slot. Thus, current OLTs may incorrectly process the optical data as having a binary logic high state, resulting in incorrect or inaccurately processed data. Inaccurately detected or processed data can lead to erroneous processing of the received data signal by receiver circuitry.
Embodiments of the present invention advantageously provide an optical and/or optoelectronic receiver and/or transceiver capable of quickly and reliably detecting data packets. For example, the present invention can be used to distinguish a data signal from interference (e.g., a noise signal or a rogue data transmission), thereby increasing the reliability of data signal detection in optical and/or optoelectronic receivers and/or transceivers. Additionally, embodiments of the present invention can allow for increased voltage threshold control. These and other advantages of the present invention will become readily apparent from the detailed description of preferred embodiments below.
This “Discussion of the Background” section is provided for background information only. The statements in this “Discussion of the Background” are not an admission that the subject matter disclosed in this “Discussion of the Background” section constitutes prior art to the present disclosure, and no part of this “Discussion of the Background” section may be used as an admission that any part of this application, including this “Discussion of the Background” section, constitutes prior art to the present disclosure.